The invention relates to a termination for securing reinforcement elements from a pipeline or a cable to an end termination.
The invention moreover relates to a use of the end termination.
Usually, flexible reinforced pipes, here called pipelines, of the above-mentioned type comprise an inner liner which forms a barrier to the outflow of the fluid that is transported through the pipe.
The inner liner is wound with one or more reinforcement layers which are not chemically bonded to the inner liner, but can move relatively to it, which ensures the flexibility of the pipeline during laying and in operation.
Externally on the reinforcement layers there is provided an outer sheath with a view to forming a barrier to the inflow of fluids from the surroundings of the pipeline to the reinforcement layers. To prevent collapse of the inner liner, it is frequently lined with a flexible, wound pipe, a so-called carcass.
The above-mentioned type of flexible pipelines is used inter alia for transporting liquids and gases at different water depths.
In particular, they are used in situations where very great or varying water pressures prevail along the longitudinal axis of the pipe. By way of example, mention may be made of riser pipes which extend from the sea bed and up to an installation at or near the surface of the sea.
Additionally, this type of pipelines is used inter alia between installations which are placed on the sea bed at a great depth, or between installations near the surface of the sea.
Some of the reinforcement layers, more particularly those which are used as compressive reinforcement, are frequently constructed such that they comprise profiles of metal. These profiles, when wound at a great angle relative to the longitudinal axis of the pipe, will be capable of absorbing radial compressive or tensile stresses that occur because of external or internal pressures in the pipeline. The profiles thus prevent collapse or bursting of the pipeline because of pressure impacts, and are therefore called compressive reinforcement elements.
In contrast, profiles wound at a small angle relative to the longitudinal axis of the pipeline, will not be capable of absorbing radial forces of importance, but will be capable of absorbing forces acting along the longitudinal axis of the pipeline. Profiles absorbing forces along the longitudinal axis of the pipeline are made of steel in conventional pipes. If they are made of a fibre-reinforced material, it is possible for the profiles to be composed of a reinforcement element or a plurality of reinforcement elements which are combined to a profile.
Below, the term tensile reinforcement elements will be used for the smallest, homogeneous, macroscopic, load-carrying part of a profile. Thus, a conventional profile will consist precisely of a tensile reinforcement element made of steel. Other more atypical profiles may be composed of a tensile reinforcement element or of a larger number of tensile reinforcement elements which are e.g. kept together as a unit by a polymer matrix.
A problem associated with the use of tensile reinforcement elements is that these must be secured at the ends of the pipeline, more particularly at the end terminations of the pipeline.
According to traditional methods, where the tensile reinforcement elements are made of steel, this attachment is provided by welding the individual reinforcement elements to the end termination.
WO 94/18585 A1 discloses a method of securing a signal-carrying cable to an end termination, said cable being surrounded by one or more tensile reinforcement elements. These elements are moreover surrounded by a cable sheath. The end termination consists of a housing which is characterized in that a locking through hole is provided in it.
Mechanical locking of the cable to the end termination is provided in that a tubular spreader element is moved down around the signal-carrying part of the cable, so that the tensile reinforcement elements and the cable sheath are pressed against the inner side of the locking hole, which results in mechanical locking of reinforcement elements and cable sheath. Subsequently, the remaining free volume is filled with a curing mass, typically thermosetting-plastics. A tensile relief is built in this manner, which operates without a critical mechanical load being applied to the signal-carrying cable.
Now, the object of the present invention is to provide a termination for individually securing relief reinforcement elements, made of an anisotropic, fibre-reinforced material, to an end termination, providing a much stronger attachment than known before.
The object of the invention is achieved in that the end termination is provided with a plurality of locking holes in which the tensile reinforcement elements are locked.
The individual locking holes are characterized in that the locking holes are separatly formed by a single hole with the same or a varying diameter.
It is an advantage if the locking holes separately consist of at least two cylindrical hole sections, where at least one hole section has a larger diameter than another hole section, as the tensile reinforcement elements can hereby be fixed easily.
Expediently, the locking is carried out in that the locking takes place by means of a local cross-sectional increase of the tensile reinforcement elements, which can be performed easily by providing the cross-sectional increase by insertion of a spreader element in to the tensile reinforcement elements.
To increase the strength of the attachment additionally, it is an advantage if the locking hole is filled with a curing mass. This provides the advantage that the locking hole with spreader element and curing mass is particularly suitable as a tension-absorbing unit having a great tension-absorbing capacity.
To improve the production-technical conditions additionally, it is an advantage if the cross-sectional increase is provided in a part of the locking hole which does not have the smallest cross-sectional area.
For some production-technical conditions it may also be an advantage that the cross-sectional increase in the tensile reinforcement element is provided outside the locking hole by means of the spreader element.
In other conditions, it will be more expedient if the cross-sectional increase of the tensile reinforcement element is provided in the locking hole more particularly by mounting in the locking hole a collar of a metal having a ductility that allows deformation of it during assembly and in use of the tensile reinforcement element.
To minimize local mechanical impacts on the reinforcement element where this is in mechanical contact with the locking holes, the collar may be made of a ductile material. If the ductile collar is loaded beyond its yield point, it will be deformed, resulting in a larger engagement face between locking hole and reinforcement element.
Expediently, the locking holes are formed such that the locking holes are positioned in circular arcs which are equidistant relative to the axis of rotational symmetry of the end termination.
Preferably, the spreader element is wedge-shaped. The wedge shape ensures that the tensile reinforcement element in the tension relief is not damaged during assembly and in operation because of too great, local, mechanical stress concentrations.
The invented method and end termination differ from the art of the above-mentioned WO 94/18585 A1 in that according to the WO publication precisely one spreader element is used for securing all reinforcement elements, whereas more spreader elements are used according to the invention.
The invented method and end termination moreover differ from WO 94/18585 A1 in that the locking is provided by a local increase in the cross-sectional area of the individual reinforcement elements.
Expedient embodiments of the end termination are also defined.
As mentioned, the invention also relates to uses of the method and the end termination.
These uses are defined in claims 18 and 19.
It is noted that precisely in connection with pipelines for the transport of fluids it is of utmost importance that the mechanical structure is extremely reliable, since the impacts on such pipelines may be very great. Especially for environmental reasons, leakages because of ruptures of such pipelines cannot be tolerated.